Tag Archives: breeding

University of Delaware doctoral student Desiree Narango is researching trees and shrubs planted in the lawns of homeowners throughout the Washington, D.C., Maryland and northern Virginia areas to assess how those choices are impacting food webs.

Narango, who is working with Doug Tallamy, professor of entomology in UD’s Department of Entomology and Wildlife Ecology, is also associated with the Smithsonian Migratory Bird Center and works through a citizen-science program called “Neighborhood Nest Watch.” Narango is co-advised by Pete Marra, director of the Smithsonian Migratory Bird Center.

Through her research, Narango looks at breeding birds and the food resources they need, such as insects and caterpillars.

Different trees vary in how much food they provide birds, and Narango said she has a network of homeowners in the D.C. metropolitan area who allowed her to use their yards for her study. Over the course of the four-year study, Narango has looked at 203 yards.

One thing that has stood out to her is the sheer number of different trees that are planted in these yards.

“We focus on woody plants — so trees and shrubs — and we’ve documented over 375 different species in these 203 yards. Which is crazy,” said Narango who added that it became apparent quickly that some trees are better than others with regard to sustaining food webs.

“We just had a paper come out in the journal of Biological Conservation where we show that native trees are better at providing caterpillars for birds, which is a really important food resource,” said Narango. “Native trees are better, hands down, but even among the native trees, there are some that are better than others so things like oaks and cherries and elms are highly productive for caterpillars, so they have lots of good food for the birds.”

Narango added that there are a lot of non-native plants — such as zelkova, ginkgo and lilac — that don’t provide any resources for breeding birds.

“Those species are true non-natives so they’re not related to anything here, and they provide almost nothing in terms of caterpillars for birds,” said Narango. “There are also species like Japanese cherry and Japanese maple that are non-native but are related to our native maples and cherries. We found that those species have an average of 40 percent fewer caterpillars than the native versions of that tree. If you had a choice between a black cherry and a Japanese cherry and if you’re interested in food for birds, then you should choose the native version.”

Narango said that a problem homeowners may face when trying to select native versions of plants is that a lot of the big box stores don’t carry them.

“There are a lot of really great small nurseries that have many native plants that are productive in terms of caterpillars and are also very beautiful,” said Narango. “You definitely don’t have to sacrifice beauty to get plants that are ecologically beneficial. There’s a lot to choose from so you can have beauty, you can have fruit and then also have food for birds, too. It’s all interconnected.”

As for the most eye-opening aspect of her research, Narango said that it has to be the tremendous amount of diversity in bugs and birds in people’s backyards.

“A lot of people think you need to go to the woods to see beautiful butterflies or beautiful birds, but they’re actually in people’s backyards, too,” said Narango.

In the group’s bird surveys, they documented 98 different bird species.

Narango focuses on the Carolina chickadee and said that she would follow individual birds around to see what trees they were choosing. One of the major findings in her paper is that the number of caterpillar species a plant supports predicts how strongly chickadees prefer it.

“When these birds would choose a tree, all the other birds in the neighborhood were choosing those trees, too. So we would see these amazing warblers that don’t breed in Delaware or in D.C. but are migrating through, and they’re using all these suburban habitats on their way north. In a way, our chickadees were telling us what all of the birds want during that period,” said Narango.

As a landscaper herself, Narango added that it was surprising to see how much life happened in her own backyard when she started planting the right species.

“I planted this flower called ironweed, and the first year it was there, I had the specialist bees that use that flower and then I have caterpillars in my shrubs, and it’s really cool how quickly you can see life be attracted to your yard when you plant the right species,” she said.

(Jenna Marshall 4 August 2017; Photo Donald Brightsmith)

For more than 16 years, researchers and volunteers have been observing wildlife along the clay cliffs of Southeastern Peru’s Tambopata River. They’ve gathered data every day, logging more than 20,000 hours and building one of the most extensive datasets on tropical parrots in the world.

In a new paper published in Ibis, Elizabeth Hobson, a postdoctoral fellow with the Arizona State University-Santa Fe Institute Center for Biosocial Complex Systems, and Donald J. Brightsmith, a professor in the Texas A&M University College of Veterinary Medicine & Biomedical Sciences (CVM) and director of the Tambopata Macaw Project, begin to analyze the data from this long-term study.

In particular, the team explores the potential drivers behind geophagy—or intentional soil consumption—they’ve regularly observed in 14 different parrot species there.

This region of the Tambopata River in Southeast Peru is an ideal spot to study the nearly two-dozen parrot species that live nearby in the Amazon rainforest. In the thick foliage of the jungle, the birds are difficult to see, but when they emerge to gather up beakfuls of the sodium-rich clay soil, “it’s a crazy, screaming kaleidoscope of color,” Hobson said.

“They’re all quiet when they take flight, but in a few seconds, they all begin to scream, and some drop bits of the clay from their mouths,” said Brightsmith, who has led the Tambopata Macaw Project since 1999. “It’s an incredible experience.”

But geophagy is a somewhat confounding behavior—clay soil is basically inert.

“It doesn’t have proteins, carbohydrates, or really anything that you’d need,” Brightsmith said. “If we can understand why it’s so important to these parrots, we can learn more about the ecosystem and how it affects the other insects, birds, and mammals who also eat this soil.”

Geophagy occurs around the world and in many types of animals, and scientists have proposed many explanations for the behavior. In their paper, Hobson and Brightsmith explore the two leading theories for these Amazonian parrots—that clay soils help protect the birds from food toxins when ideal food sources are scarce and that clay soils provide necessary minerals not available in the parrots’ regular diet.

Like previous studies, their analysis suggests that toxin-protection is not a driver. But parrot geophagy there is highly correlated with breeding season, suggesting the increased nutritional demands are likely behind the soil consumption. This study also joins a large body of research suggesting that hunger for sodium, specifically, is that driver.

“There’s lots of evidence that’s pointing in that direction,” Hobson said. “Sodium in the rainforest is really rare, and the place on these clay licks most preferred by the birds also has the highest sodium content.”

Understanding how nutritional needs are—and are not—being met during breeding season becomes even more important in light of climate change, according to Brightsmith. Some of the larger macaws are already breeding right before a seasonal crash in the food supply, requiring parents take their fledgling young on long flights to find food.

“If climate change starts messing with the macaw’s food supply, it could disrupt their ability to breed,” he said.

(Science Daily, American Ornithological Society 26 July 2017)

In 1966, a U.S. Fish and Wildlife Service biologist named Chan Robbins launched an international program designed to measure changes in bird populations using volunteers recruited to count birds on pre-set routes along country roads. The result, the North American Breeding Bird Survey or BBS, is still going strong more than five decades later. This month The Condor: Ornithological Applications is publishing a special set of research papers to honor the program’s fiftieth anniversary.

Unassuming but visionary, Robbins had studied DDT’s effects on birds — his reports were edited by Rachel Carson — and he wanted to devise a way of monitoring the health of the continent’s bird populations on a large scale. The simple field protocols he developed, able to be carried out by volunteer birdwatchers, have remained largely the same since the program’s inception. Today, there are more than 4100 survey routes spanning North America from Alaska to Newfoundland, Florida, and northern Mexico.

The BBS provides long-term data for 424 species, with more limited data for an additional 122. Since data collection began in the 1960s, significantly more species have been declining than increasing. Looking at patterns of change in groups of birds sharing common attributes can be especially useful; for example, only 8 of 24 grassland bird species have seen increases. However, in the short term the picture is slightly rosier — since the survey area was expanded in 1993, 56% of the species surveyed have showed positive trends. Today, modern statistical techniques are letting ornithologists glean more insight from BBS data than ever before.

“The BBS is the only source of long-term, multi-scale population change information for more than 500 species of North American birds,” according to the USGS’s John Sauer, who has worked with the BBS since 1986 and was one of the co-editors for the special section along with Keith Pardieck and Colleen Handel, also with the USGS. “BBS results have allowed conservationists to identify bird species and regions undergoing population declines, alerting the public and scientists to population changes and facilitating the development of initiatives to better understand declines.”

The papers that make up the special section in The Condor include:

Prioritizing areas for conservation by combining six years of BBS data with remotely sensed environmental data to model the predicted distribution of seven grassland bird species in the Northern Great Plains based on their habitat needs.

Statistical approaches for model selection in BBS analyses.

Combining BBS with off-road surveys to estimate population changes for birds that breed in Alaska, where habitats are being rapidly altered due to climate change.

Using long-term BBS data to rank the vulnerability of more than 460 landbird species, set population objectives, and track progress toward meeting conservation goals.

Analyzing how well road-based BBS routes represent larger landscapes, using data from 2011 National Land Cover Database, with the conclusion that any land-cover-based roadside bias in BBS data is likely minimal.

Plus, a review of how the BBS has informed North American bird conservation since its inception.

The papers grew out of a research symposium held at last summer’s North American Ornithological Conference in Washington, DC, to commemorate 50 years of the BBS. “The BBS provides a fundamental tool for understanding breeding bird distribution and abundance. We’re pleased to publish these papers that celebrate Chan Robbins’s vision and the hard work of thousands of volunteers through the latest results and analyses,” said Philip Stouffer, Editor-in-Chief of The Condor: Ornithological Applications.

New Victoria University research suggests hormones found in New Zealand’s native plants are helping endangered native birds to breed successfully.

The study, published in Reproduction, Fertility and Development and conducted by Victoria Ph.D. graduate Dr. Catherine Davis, looks at the potential link between parrot breeding and high levels of fruiting by native plants.

“A mast year is a year when plants produce masses of edible fruit or seeds,” explains co-supervisor Dr. Janet Pitman from Victoria’s School of Biological Sciences.

“Kākāpō breed only in mast years—that’s once every three or four years. So there’s something happening in those mast years that triggers their breeding.”

Kākāpō are critically endangered, with fewer than 160 known surviving birds.

Dr. Pitman says it’s been hypothesised that kākāpō require more of the hormone oestrogen than they can produce themselves to make a fertile egg.

“We know from other studies that oestrogens present in new grass may interfere with reproduction in animals, and we know kākāpō seek out fruit from rimu to eat during mast years.

“We believe kākāpō get extra oestrogen from their diet during mast years, and rimu and other native plants provide that extra oestrogen that is key to kākāpō reproduction.”

Dr. Pitman and her research team set out to shed light on this potential hormonal link.

“We tested various native plant species for oestrogenic content—and we found that indeed there is a high amount of oestrogen in some of New Zealand’s native plants,” she says.

“We also looked at the receptivity of parrots to oestrogen. We studied the genetic makeup of the receptor that is activated by oestrogens in the New Zealand kākāpō, kea, kākā, kākāriki, the Australian cockatiel, and compared them with those in the chicken.”

“We found that all of the parrot species have a unique sequence in this receptor gene that may make them more sensitive to oestrogen, compared to other bird species or humans.”

Dr. Pitman says this suggests the oestrogen produced in native trees may provide the link between mast years and successful breeding of parrots like kākāpō.

“With further research we’re hoping to identify the specific oestrogenic settings in native plants. This information may enable a synthetic model to be produced, so we could potentially use it increase the fertility of our native parrots.”

One summer, when I was licensed to rehab wild birds, a woman brought me four tiny baby songbirds. Their nest branch had been knocked from a tree during a storm a week before. She thought her children would get a kick out of seeing and feeding nestling birds even though, as she told me, she knew that they’d eventually die.

She’d been feeding them nothing but canned dog food and didn’t know how to feed them properly, or keep them in a clean environment, so all four were caked in a disgusting mixture of dried up food and feces. I had to bathe them repeatedly over many hours to even be able to identify them. They were Red-eyed Vireos. Their little bodies, including their heads and, in one case, their eyes, had been so completely encased in crusted filth for so many days that they literally could not grow.

She brought them to me just before the Fourth of July weekend, because she was expecting company and also, she confided, because she did not want her children to experience the sadness of them dying. She drove off feeling virtuous for saving her children from that. I’m sure when she got home she told them that the birds were being taken care of and would all fly off happily.

Meanwhile, my children and I were the ones left to experience the sadness of death. The tiniest nestling lasted barely a day, but all of them were beyond the point of no return when I got them.

They’d not received vitamins or other essential elements of their diets to ensure proper bone development. The people must have been feeding the chicks chunks of dog food that were much too large to be swallowed. The poor things’ heads were so encrusted that their brains had not been allowed to grow properly. They were kept on flat paper towels that were not changed frequently enough.

In nature, their parents would have collected the fecal sacs the moment they were produced. Baby birds poop almost immediately after swallowing while the parent who fed it is sure to still be present. That makes that part of taking care of baby birds easy for people, too. The back end of two of these nestlings was so encrusted that their droppings couldn’t get out of their bodies. I still shudder remembering this, and have mercifully forgotten a lot of other details. In the end, none of them made it. My children were heartbroken.

A biblical maxim says that man cannot live by bread alone. The metaphor is not about the need for balanced nutrition—it’s about how human beings cannot thrive when only the needs of their stomachs are addressed. Keeping baby birds clean and comfortable is as essential as food. Also, from the moment baby birds hatch, they are learning about their world and interacting with it. Many baby birds of migratory species, days or a week before they even leave the nest, start to learn star patterns. They’ll use the one fixed star in the sky, Polaris, as a compass point when they take off for the tropics.

Wind and precipitation play a crucial role in advancing or delaying the breeding cycles of North American tree swallows, according to the results of a new University of Colorado Boulder-led study.

The research, which appears today in the journal Proceedings of the Royal Society B, sheds new light on how wet, windy weather can affect tree swallow nesting and underscores the importance of considering factors beyond temperature when examining how climate change might affect species’ biological niche.

Over the past decade and a half, the average egg hatching date for tree swallows—a common migratory bird species that winters in temperate southern climates before nesting in the spring at sites across North America, including the sub-Arctic regions covered in the study—has shifted earlier in the year by an average of six days. This change is similar to, but considerably greater than, changes seen in more southerly sites and until now has been believed to correlate with rising temperatures.

However, when CU Boulder researchers tested how swallow nesting data from two different Alaskan sites corresponded with both daily and seasonal climate indicators like the number of windy days, days with measureable precipitation and average daily temperature, they found that windiness (or lack thereof) had the most consistent correlation with swallow breeding patterns over time.

“We expected that temperature and precipitation would be much more strongly predictive than wind,” said Daniel Doak, a professor in CU Boulder’s Environmental Studies Program and the co-author of the new research. “The study demonstrates that fine-scale climate effects are important to consider when thinking about what’s going to affect a species.”

The study developed as a result of a CU Boulder undergraduate’s research efforts. Rachel Irons, then a junior in the Department of Ecology and Evolutionary Biology, received a UROP grant and worked with the Alaska Department of Fish and Game on a long-term tree swallow nesting study to fulfill her senior thesis requirements.

“Swallow phenology in Alaska is shifting at twice the rate of the continental U.S.,” said Irons, who is the lead author of the new paper. “I figured it was related to temperature, but I added in wind and precipitation measurements just to get the whole climate picture.”

The results showed that a long-term decline in windiness (and to a more variable extent, rain) in central Alaska over the past decade-plus correlated with the birds’ earlier breeding much more strongly than temperature, indicating that wet, windy spring weather that may have delayed egg laying in the past is now less of an impediment for the swallows.

The authors noted that while it is not necessarily surprising that wind and rain would affect an aerial foraging species like tree swallows, the findings emphasize the need to broaden the scope of consideration when making predictions about which climate mechanisms will influence population ecology.

“This shows that our initial intuitions are not always good about what’s going to impact these birds and their patterns,” said Doak.